U.S. patent number 7,726,767 [Application Number 11/762,460] was granted by the patent office on 2010-06-01 for image processing method and ink jet printing apparatus.
This patent grant is currently assigned to Canon Kabushiki Kaisha. Invention is credited to Eri Noguchi, Takashi Ochiai, Tsuyoshi Shibata, Hiromitsu Yamaguchi.
United States Patent |
7,726,767 |
Noguchi , et al. |
June 1, 2010 |
Image processing method and ink jet printing apparatus
Abstract
There is provided an ink jet printing apparatus capable of
printing an image having few joining stripes. Dot count is
performed regarding an image printed in the vicinity of the joining
stripe, and print duty is judged. Next, a dot count value is
determined from the print duty. Then, a print data correction rank
is determined beforehand in accordance with properties of the
printing apparatus, and image data to be printed in the vicinity of
the joining stripe is added or thinned out. Thus, an image can be
printed which has few black and white stripes.
Inventors: |
Noguchi; Eri (Yokohama,
JP), Shibata; Tsuyoshi (Yokohama, JP),
Yamaguchi; Hiromitsu (Yokohama, JP), Ochiai;
Takashi (Tokyo, JP) |
Assignee: |
Canon Kabushiki Kaisha (Tokyo,
JP)
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Family
ID: |
38861097 |
Appl.
No.: |
11/762,460 |
Filed: |
June 13, 2007 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20070291062 A1 |
Dec 20, 2007 |
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Foreign Application Priority Data
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Jun 20, 2006 [JP] |
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2006-170462 |
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Current U.S.
Class: |
347/19; 347/41;
347/15 |
Current CPC
Class: |
B41J
2/2132 (20130101); G06K 15/107 (20130101) |
Current International
Class: |
B41J
29/393 (20060101) |
Field of
Search: |
;347/15,41,43,19,40 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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8-025693 |
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Jan 1996 |
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JP |
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2002-036524 |
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Feb 2002 |
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JP |
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Primary Examiner: Nguyen; Lamson D
Attorney, Agent or Firm: Fitzpatrick, Cella, Harper &
Scinto
Claims
What is claimed is:
1. An image processing method for generating print data for an ink
jet printing apparatus, which performs printing by making a
printing head having a plurality of nozzles for ejecting ink scan a
print medium, and ejecting an ink droplet from the printing head
onto the print medium to form dots, said method comprising: a step
of, based on print data for each of two scans forming image print
regions adjacent to each other, obtaining information on a forming
amount of dots which is indicated by print data corresponding to a
predetermined region including a boundary between the image print
regions adjacent to each other; and a step of correcting print
data, which corresponds to a vicinity region of the boundary, of
the print data for a different scan from the two scans, based on
the information obtained in said obtaining step.
2. The image processing method according to claim 1, wherein the
information on the forming amount of dots is information showing a
number of forming dots.
3. The image processing method according to claim 1, wherein the
vicinity region is included in the predetermined region and is
smaller than the predetermined region.
4. An ink jet printing apparatus for generating print data for an
ink jet printing apparatus, which performs printing by making a
printing head having a plurality of nozzles for ejecting ink scan a
print medium, and ejecting an ink droplet from the printing head
onto the print medium to form dots, comprising: an obtaining unit
configured to, based on print data for each of two scans forming
image print regions adjacent to each other, obtain information on a
forming amount of dots which is indicated by print data
corresponding to a predetermined region including a boundary
between the image print regions adjacent to each other; and a
correcting unit configured to correct print data, which corresponds
to a vicinity region of the boundary, of the print data for a
different scan from the two scans, based on the information
obtained by said obtaining unit.
5. The ink jet printing apparatus according to claim 4, wherein the
vicinity region is included in the predetermined region and is
smaller than the predetermined region.
6. The ink jet printing apparatus according to claim 4, wherein the
information on the forming amount of dots is information showing a
number of forming dots.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image processing method and an
ink jet printing apparatus, more particularly, it relates to an
image processing method and ink jet printing apparatus for
performing image processing for reducing a joining stripe caused by
scans of a printing head in image printing.
2. Description of the Related Art
Recently, the need for high speed printing has increased in
printing to a print medium by a printing apparatus. In an ink jet
printing apparatus for printing by ejecting ink droplets, in order
to print one line of dots constituting an image, a multi-pass
printing method is employed for printing by making a printing head
scan to a line a plurality of times.
The multi-pass printing method has an advantage that high image
quality printing can be realized. However, in order to realize high
speed printing, it is effective to reduce the number of passes that
is the number of scans of a carriage necessary for completion of
printing for one line. That is, since a paper conveyance amount per
one time becomes small as the number of passes becomes large, the
printing speed per one line is decreased. On the other hand, since
the paper conveyance amount per one time becomes large as the
number of passes becomes small, the printing speed per one line is
increased. For example, comparing four-pass printing with two-pass
printing, about two times the speed is realized if two-pass
printing instead of four-pass printing is performed. Accordingly,
as the number of passes becomes small, the number of scans of the
carriage required for printing to a predetermined region of a piece
of print paper or the like is decreased, and the paper conveyance
amount per one time becomes large, and consequently a time required
for a predetermined printing is shortened.
In the multi-pass printing method, since printing is performed to a
region for one band, which is a band-shaped image region, by
multiple scanning, a joining stripe is likely to be caused at a
joining part between the bands.
FIG. 1 is a view showing an image region in which the two-pass
printing is performed. In the ink jet printing apparatus, the
carriage scans in a direction orthogonal to an arrangement
direction of ink ejecting ports so that printing is performed, and
thus a band-shaped image print region is formed every scanning.
When printing is performed on the print medium, for example, plain
paper on which ink easily bleeds, a black joining stripe caused by
the bleeding of the ink at the joining part between the bands can
be visually checked although the degrees of the stripes are
different from each other depending on the properties of ink
droplets or print mediums. In particular, when the number of passes
is reduced and printing is performed, a clear joining stripe can be
visually checked, and print quality is lowered. That is, the number
of dots to be printed on the print medium by the scanning in
two-pass printing becomes about twice that in four-pass printing,
and consequently duty, which is the rate of dots to the region,
also becomes approximately twice. Therefore, a clearer black
joining stripe can be visually checked as the number of passes
becomes smaller.
As a method for realizing a high image quality by removing the
black joining stripe, a method disclosed in Japanese Patent
Laid-Open No. 2002-036524 is conventionally known that printing is
performed per a band by repeating main scans of the printing head,
and that print data is subjected to a thinning-out processing
corresponding to a print amount of a region in the vicinity of the
joining part. More specifically, dots printed on the region in the
vicinity of the joining part are counted, and the thinning-out
processing is performed corresponding to the counted value.
Additionally, in Japanese Patent Laid-Open No. 8-025693 (1996), it
is disclosed that the joining stripe is reduced in a one-pass
printing method for printing to a certain region by making the
carriage scan only once. That is, a printing method is disclosed
that images to be each printed by scanning are partly overlapped
with each other, and complement the overlapped region by a random
mask pattern between scanning.
However, the conventional method disclosed in Japanese Patent
Laid-Open No. 2002-036524, is applicable to the case where the
joining stripe is black, but not applicable to the case where the
joining stripe is white. The joining stripe is caused by low
precision of the paper conveyance, end nozzle dot deflection or the
like unique to the printing apparatus in addition to the ink bleed,
and the white joining stripe is sometimes caused at the joining
part. However, the conventional method cannot solve the above
problem. Here, the end nozzle dot deflection indicates a phenomenon
that ink droplets landing position by a nozzle arranged on both
ends of a plurality of arranged nozzles deviate toward a center
axis of the printing head. Regarding the end nozzle dot deflection
phenomenon, it is observed that the deflection of the landing
position of the ink droplets is large as the duty in each scanning
is high, or the size of the ink droplets is small. In particular,
when the ink droplets are not more than 2.8 pl, the end nozzle dot
deflection becomes large. Accordingly, the end nozzle dot
deflection becomes large in the two-pass printing since duty of ink
in the two-pass printing is larger than that in the four-pass
printing. Thus, the white joining stripe is likely to occur at the
joining part between the bands. In particular, a clear white
joining stripe can be visually checked on a print medium such as
photo-paper on which the ink hardly bleeds, and the image quality
is lowered.
Additionally, in the conventional methods disclosed in Japanese
Patent Laid-Open Nos. 2002-036524 and 8-025693 (1996), image data
for the nozzles is corrected, the nozzles being arranged at both
ends of the nozzle arrangement line. In this case, since the ink
droplets ejected from the nozzles arranged at both ends are
affected by the end nozzle dot deflection, a desired correction is
hardly applied to the image data, and the joining stripe is not
always reduced. In particular, such precision is insufficient for
printed images such as photographs and graphics for which a high
quality image is required.
SUMMARY OF THE INVENTION
In view of the above problems, the present invention was carried
out, and it is an object of the present invention to provide an
image processing method and ink jet printing apparatus for reducing
a joining stripe and capable of obtaining an excellent printed
image in printing an image by repeating a main scanning. More
specifically, the present invention aims at providing an image
processing method and ink jet printing apparatus for reducing the
joining stripe and capable of obtaining an excellent printed image
even by a one-pass printing method or multi-pass printing method
using a small number of passes.
In order to achieve the above object, in the present invention, an
image processing method for generating print data for an ink jet
printing apparatus which performs printing by making a printing
head having a plurality of nozzles for ejecting ink scan a print
medium, and ejecting an ink droplet from the printing head onto the
print medium so that the ink droplet forms into a dot, said method
comprising: a step of calculating duty of dots from print data for
nozzles corresponding to a predetermined vicinity of a boundary
between image print regions adjacent to each other in print data of
each of two scans forming the adjacent image print regions; and, a
step of correcting print data for nozzles other than the nozzles
corresponding to the predetermined vicinity of the boundary in
print data in either of the two scans, or scanning other than the
two scans, and adding or thinning out a dot, corresponding to the
calculated duty of dots.
According to the above constitution, since the dots on the print
region are counted so that the image processing is performed for
increasing or decreasing image density of the joining part, an
excellent printed image having few joining stripes can be
constantly obtained even by the one-pass printing method or the
multi-pass printing method using the small number of passes.
Further features of the present invention will become apparent from
the following description of exemplary embodiments (with reference
to the attached drawings).
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a view showing an image region in the case of performing
two-pass printing;
FIG. 2 is a perspective view of an ink jet printing apparatus
according to a first embodiment of the present invention;
FIG. 3 is a schematic view of a printing head used for the ink jet
printing apparatus shown in FIG. 2;
FIG. 4 is a view showing nozzle lines of the printing head of the
first embodiment of the present invention;
FIG. 5 is a block diagram illustrating a control circuit used for
the ink jet printing apparatus according to the first embodiment of
the present invention;
FIG. 6 is a view showing an image region in the case of performing
the two-pass printing in the first embodiment of the present
invention;
FIG. 7 is a view showing a print data correction processing region
in the case of performing the two-pass printing in the first
embodiment of the present invention;
FIG. 8 is a flowchart indicating image processing performed in a
host computer of the first embodiment of the present invention;
FIG. 9 is a view showing a dot count region in the case of
performing the two-pass printing in the first embodiment of the
present invention;
FIG. 10 is a view showing a print data correction processing region
in the case of performing the two-pass printing in the first
embodiment of the present invention;
FIG. 11 is a view showing joining stripe density in the first
embodiment of the present invention;
FIG. 12 is a graph indicating a relationship between print duty and
the joining stripe density in the first embodiment of the present
invention;
FIG. 13 is a graph indicating a relationship between the print duty
and a dot count value in the first embodiment of the present
invention;
FIG. 14 is a graph indicating a relationship between the dot count
value and a print data correction rank in the first embodiment of
the present invention;
FIG. 15 is a view showing a print data correction region, in which
print data is added or thinned out, in the case where the
correction rank is 5 in the first embodiment of the present
invention;
FIG. 16 is a view showing ejecting port lines of a printing head of
a second embodiment of the present invention;
FIG. 17 is a view showing an image region in the case of performing
one-pass printing in the second embodiment of the present
invention;
FIG. 18 is a flowchart indicating image processing performed in a
host computer of the second embodiment of the present
invention;
FIG. 19 is a view showing a dot count region in the case of
performing the one-pass printing in the second embodiment of the
present invention; and
FIG. 20 is a view showing ejecting port lines of a printing head of
a third embodiment of the present invention.
DESCRIPTION OF THE EMBODIMENTS
Embodiments of the present invention will be described below with
reference to the accompanying drawings.
First Embodiment
FIG. 2 is a perspective view of an ink jet printing apparatus
according to an embodiment of the present invention. The reference
symbols 1A, 1B and 1C each denotes an ink cartridge, and 502
denotes a carriage. The ink cartridges 1A to 1C and a printing head
for ejecting ink (not shown) are detachably mounted on the carriage
502. The printing head has electro-thermo converters, generates
thermal energy with the electro-thermo converters, and ejects the
ink from an ink ejecting port. That is, the ink is ejected from the
ink ejecting port, and printing is performed, with use of pressure
variations generated owing to the growth and contraction of bubbles
by film boiling generated by the thermal energy applied from the
electro-thermo converter.
The ink cartridges 1A to 1C respectively have ink tanks different
in each color, and is contained ink of, for example, cyan, magenta
and yellow. The carriage 502 includes a connector holder (not
shown) for transmitting a driving signal to the printing head.
Additionally, the carriage 502 is driven via a motor pulley 505, a
driven pulley 506 and a timing belt 507, and reciprocates along a
guide shaft 503 by a main scanning motor 504, the guide shaft being
provided in a main scanning direction. A print medium 508 such as
print paper or a plastic thin plate is supported by a platen (not
shown) so as to form a flat print surface relative to the ink
ejecting port provided in the printing head, and carried to a
position opposite to an ejecting port surface of the printing head
by rotation of two sets of carriage rollers.
FIG. 3 is a schematic view of the printing head used for the ink
jet printing apparatus shown in FIG. 2. The printing head includes
an ink ejecting port 621 which is opposite to the print medium 508
at a predetermined interval of about 0.5 to 2 mm. 512 nozzles 622
are provided at a pitch corresponding to 2400 dpi in the ink
ejecting port. Inside of the printing head, an electro-thermo
converter 625 such as an exothermic resistor for generating energy
for ink ejecting is arranged along a wall surface of each flow path
624 communicating a common liquid chamber 623 with each ejecting
port of the nozzle 622.
FIG. 4 is a view of the printing head, which is shown in FIG. 2 and
FIG. 3, viewed from the side opposite to the print medium. The 512
nozzles for ejecting ink are arranged in a sub-scanning direction,
and the nozzle lines of yellow (Y), magenta (M), and cyan (C) are
arranged in this order in the main scanning direction, in a surface
opposite to the print medium. In the embodiment, numbers 1 to 512
are assigned to the nozzles arranged in the sub-scanning
direction.
FIG. 5 is a block diagram illustrating a control circuit used for
the ink jet printing apparatus shown in FIG. 2. A controller 700,
which is a main controlling part, includes: a CPU 701 having a
microcomputer form; a ROM 702 in which a fixed data such as a
program and a predetermined table is stored; and a RAM 703 in which
a region for developing image data and a working region are
provided. Additionally, the controller 700 performs image
processing such as addition or thinning-out processing of print
data described below. A host unit 704 is a computer for performing
creation and processing of image data, and also a supply source of
image data such as a reader for image reading. Commands and status
signals, etc., of the image data, are transmitted/received to/from
the controller 700 via an interface 709.
The reference numeral 705 denotes an operating part constituted by
a switch group for receiving instructions inputted from an
operator, and includes: a power switch 706; a switch for issuing an
instruction of starting printing; a switch 708 for issuing an
instruction of starting suction recovery; and the like.
The reference numeral 710 denotes a head driver, and is a driver
for driving an ejection heater 711 of a printing head 1 depending
on the print data, etc. The head driver 710 has a shift register
for making the print data correspond to a position of the ejection
heater 711 and aligning the print data, and a latch circuit for
latching the print data at a proper timing. Further, the head
driver 710 includes: logic circuit elements for running the
ejection heater in synchronization with a driving timing signal; a
timing setting part for properly setting a driving timing (ejecting
timing) for dot formation positioning; and the like.
A sub-heater 712 is provided on the printing head 1. The sub-heater
712 performs temperature adjustment for stabilizing an ejecting
property of the ink. The sub-heater 712 may be formed on the
ejection heater 711 and a substrate of the printing head, or
attached to a printing head body or a printing head cartridge.
The reference numerals 713 and 715 each denotes a motor driver, and
drive a main scanning motor 714 and a sub-scanning motor 716
respectively.
FIG. 6 is a view showing a white joining stripe in the case where
printing is performed with an ink jet printing apparatus for
printing by two-pass printing. A region 6A indicates a region in
which an image is formed by two scans. When print duty of the
region is 100%, print duty of each main scanning is about 50% if
the print data is distributed to each main scanning by a random
mask.
The reference symbol 6B indicates a paper conveyance amount, and
the paper conveyance amount is equal to the length of a printing
head 6C and fixed. The printing head used for the embodiment
includes the 512 nozzles at the pitch corresponding to 2400 dpi,
and the jet amount is about 1.5 pl. Here, a print width 6D actually
printed is shorter than the paper conveyance amount by 20 .mu.m due
to the end nozzle dot deflection of the ejecting ports at both
ends, and a joining stripe 6E becomes a white stripe having a width
of 20 .mu.m. The white stripe corresponds to about two pixels in
the pitch corresponding to 2400 dpi.
FIG. 7 is a view showing a print data correction processing region
in the case of performing the two-pass printing. As shown in FIG.
7, the vicinity of the joining part formed by n-th scanning and
n+2-th scanning is divided into certain unit regions, dots of each
ink color are counted for each region, and duty of the ink for the
unit region is decided. Then, a data addition or thinning-out
amount in the print data correction processing region is determined
for each color from a dot count value for each region obtained by
counting the dots and a relationship between a given duty of the
ink and the print data addition or thinning-out processing. The
print data addition or thinning-out processing is performed in
accordance with the determined data addition or thinning-out
amount.
The print data correction processing region is, for example, four
pixels in the sub-scanning direction and all pixels in the main
scanning direction, and is in the vicinity of joining part, in
n+1-th scanning on the joining part. That is, the correction region
in the embodiment corresponds to the four nozzles positioned at the
approximate center in the nozzle arrangement line of the printing
head, data for four pixels. According to the embodiment, the print
data for the nozzles, which are positioned at places other than the
ends in the nozzle arrangement line in the printing head for
performing scanning, is corrected in the two scans forming the
joining parts and another scanning. That is, the print data
correction, which is addition or thinning-out of dot data, is
performed corresponding to the dot duty of a predetermined vicinity
of the joining part. Thus, a proper correction can be performed
regardless of the end nozzle dot deflection generated for the end
nozzle. It is desirable that the width of the region is larger than
that of the maximum joining stripe.
FIG. 8 is a flowchart of the image processing of the embodiment,
and shows a flow from reception of the print data of the first
scanning to end of print data processing in the image processing
for one band. In the flowchart, a state, where binary print data is
set by the scanning by a mask of the two-pass, is represented as
Start.
First, the print data of the first scanning and third scanning
forming the joining part is received (Step S1).
FIG. 9 is a view showing a dot count region in the case of
performing the two-pass printing in the embodiment of the present
invention. In Step S2, dots of the print data in the dot count
region of each scanning shown in FIG. 9 are counted. The dot count
indicates measuring the amount of the binary print data, and
corresponds to the print duty.
As shown in FIG. 9, the region, in which the dot count is to be
performed by one processing, is 4 pixels on each side of the
joining part formed by the first scanning and third scanning in the
sub-scanning direction, and is 24 pixels in the main scanning
direction.
The dot count is performed, and thus a data correction rank is
determined based on the print duty by the following method (Step
S3). Then, the print data of the second scanning is received (Step
S4), and the image processing such as addition or thinning-out of
print data of the second scanning is performed based on the
correction rank (Step S5). In the image processing, a given count
value is referenced whenever the print data is received, and
addition or thinning-out of print data is performed when the count
value is 1, and is not performed when the count value is 0. The
processing is performed by the band (Step S6), and the processing
for the next band is started after the processing for the band
ends. After the correction to the print data ends, printing is
performed.
FIG. 10 is a view showing a print data correction region of the
second scanning. The region, in which the print data is to be
corrected, is a few pixels across the joining part of the first
scanning and third scanning. The correction region in the
embodiment is print data for four pixels which correspond to the
four nozzles, nozzle Nos. 254 to 257. Moreover, the image density
of the second scanning may be increased or decreased based on the
dot count value, and therefore the correction region may not be
pixels corresponding to the nozzles arranged at the center part of
the printing head of the second scanning. However, it is preferable
that printing is performed by nozzles other than the nozzles
arranged at both ends of the nozzle arrangement line.
FIG. 11 is a view showing the density of the joining stripe. The
joining stripe density indicates a difference between the density
of the joining stripe in the carriage scanning direction and the
density of the region in which the image is formed by the two
scans, and thus the degrees of the joining stripe can be evaluated.
When the joining stripe density is 0, no joining stripe appears.
Additionally, the white stripe appears when the joining stripe
density is positive, and the black stripe appears when it is
negative. For example, the white stripe is shown in FIG. 11.
FIG. 12 is a graph indicating a relationship between the joining
stripe density and the print duty. The relationship is unique to
the printing apparatus, and depends on a carriage scanning speed,
the print medium, the number of printing heads, the distance
between the print medium and the printing head and the like.
Accordingly, if the relationship between the joining stripe density
and the print duty is properly grasped, the rank of the addition or
thinning-out of print data can be set at high precision. The print
duty and the rank of the addition or thinning-out of print data are
set based on the relationship between the joining stripe density
and the print duty.
FIG. 13 is a graph indicating a relationship between the print duty
and the dot count value. The level of the dot count value is
constituted by eight stages corresponding to the print duty. That
is, the dot count value is 1 when the print duty is not less than
0% and less than 12.5%, it is 2 when the print duty is not less
than 12.5% and less than 25%, and it increases one by one when the
print duty increases by 12.5%. For example, when the print duty is
50%, the dot count value is 5. Moreover, although eight stages are
set in the embodiment, the number of stages is not limited to
eight.
FIG. 14 is a graph indicating a relationship between the dot count
value and the print data correction rank. Each print data
correction rank is determined in advance based on the property
unique to the printing apparatus shown in FIG. 12. The print data
correction rank corresponds to the dot count value so that the
joining stripe density becomes 0 or about 0.
FIG. 15 is a view showing a print data correction region in which
print data is added or thinned out in the case where the correction
rank is 5. When the dot count value is 5, the print data correction
rank is 5. A square represents the pixel, a black square indicates
the addition of print data, and a white square indicates the
thinning-out of print data. As the correction rank rises, the
number of black squares increases, and as the correction rank
lowers, the number of white squares increases.
All pixels are subjected to the above processing in the main
scanning direction so that a high quality image having no
conspicuous joining stripe can be obtained by the printing method
using a small number of passes.
Moreover, although the means for adding or thinning out print data
is employed in the embodiment, print density may be increased or
decreased by, for example, means for increasing or decreasing the
ejection amount of the ink.
Second Embodiment
Serial scanning type two-pass printing is cited in the first
embodiment. However, the present invention is applicable to
one-pass printing.
FIG. 16 is a view of a printing head used for the embodiment viewed
from the side opposite to the print medium. The nozzle lines of
yellow (Y), magenta (M), cyan (C), yellow (Y), magenta (M) and cyan
(C) are arranged in the surface opposite to the print medium in the
main scanning direction in this order. The three nozzle lines
arranged on the left side in FIG. 16 is represented as a left line
16A, and the three nozzle lines arranged on the right side is
represented as a right line 16B. The left line 16A and right line
16B are shifted from each other by a difference H in a nozzle
arrangement direction. Preferably, the difference H is within the
length of the ejecting port line of three pixels or more. However,
the number of ejecting ports of the left line may be the same as or
different from that of the right line, and the numbers of the
ejecting ports in nozzle groups 16C, 16D may be different from each
other. The embodiment will be described below with use of the
nozzle numbers shown in FIG. 16.
FIG. 17 is a view showing a printed image in the case where an
image is printed by one-pass printing. In FIG. 17, only the nozzle
line of magenta (M) is shown, and the nozzle lines of the other
colors are not shown. The reference symbol 17A denotes the printed
image, and the stripe is caused by the end nozzle dot deflection of
the nozzles arranged at the ends of the left line and the right
line in the sub-scanning direction.
FIG. 18 is a flowchart indicating image processing of the
embodiment, and indicates a flow from reception of the print data
for one scanning to the end of the print data processing.
First, print data for the left lines of the first scanning and
second scanning is received (Step S11). Next, the dot count is
performed in a dot count region regarding the print data for left
lines of the first scanning and second scanning.
As shown in FIG. 19, the region in which the dot count is performed
by one processing is 4 pixels on each side of a joining part formed
by the first scanning and second scanning in the sub-scanning
direction, and is 24 pixels in the main scanning direction. That
is, in the sub-scanning direction, dots corresponding to ink
droplets ejected from the nozzles Nos. 17, 19, 21 and 23 arranged
in the left line are counted in the first scanning, and dots
corresponding to ink droplets ejected from the nozzles Nos. 1, 3, 5
and 7 arranged in the left line are counted in the second
scanning.
Next, the print data correction rank is determined (Step S3) like
the description of the first embodiment, and the print data is
corrected in the print data correction region of the right line of
the first scanning. The print data for the left line and the print
data for the right line are printed with thinning-out patterns
different from each other so as to be complementary to each other
in the printed image, and the image is printed. The nozzle group
16C is not used in the first scanning, and the nozzle group 16D is
not used in the second scanning. For example, when the image shown
in FIG. 17 is printed, none of the nozzles Nos. 1, 3, 5, 7 and 9 of
the M left nozzle line is used in the first scanning. Additionally,
none of the nozzles Nos. 1016, 1018, 1020, 1022 and 1024 of the M
right nozzle line is used in the second scanning.
Print data for four pixels corresponding to ink droplets to be
ejected from the nozzles Nos. 1012, 1014, 1016 and 1018 of the M
right nozzle line is corrected in the first scanning. Next, print
data for four pixels corresponding to ink droplets to be ejected
from the nozzles Nos. 5, 7, 9 and 11 of the M left nozzle line is
corrected in the second scanning.
All pixels are subjected to the above processing in the main
scanning direction so that a high quality image having no
conspicuous joining stripe can be obtained even in the one-pass
printing. Moreover, image printing may be performed with use of the
nozzle groups 16C, 16D.
Third Embodiment
The present invention is applicable to an ink jet printing
apparatus provided with an ink ejecting port line having dummy
nozzles.
FIG. 20 is a view showing the ink ejecting port line having the
dummy nozzles. The ejecting port line shown in FIG. 20 has 16
nozzles at the pitch corresponding to 2400 dpi. Three nozzles 20A
arranged at each end are the dummy nozzles, and not used in image
printing. For example, in the ink jet printing apparatus, when the
ink jet printing head is heated by a heater for ejecting the ink,
the temperature of the end nozzles is sometimes raised. In this
case, an ink head is sometimes used in which the dummy nozzles are
arranged at both ends thereof.
The present invention is applicable to such a printing head. That
is, although a stripe is sometimes caused between an image printed
with ink ejected from an ink nozzle 20D in the first scanning and
an image printed with ink ejected from an ink nozzle 20C, the
present invention is applicable to this case.
[Other]
The present invention has an excellent effect on a printing
apparatus provided with a printing head employing a method for
changing a state of the ink by the thermal energy and ejecting the
ink, the method being especially selected from ink jet printing
methods. According to the method, high-density printing and
high-precision printing can be realized.
While the present invention has been described with reference to
exemplary embodiments, it is to be understood that the invention is
not limited to the disclosed exemplary embodiments. The scope of
the following claims is to be accorded the broadest interpretation
so as to encompass all such modifications and equivalent structures
and functions.
This application claims the benefit of Japanese Patent Application
No. 2006-170462, filed Jun. 20, 2006, which is hereby incorporated
by reference herein in its entirety.
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